Jump List not Showing

I have a list of "Contact" objects and it displays in groups but does not display the jump list. Here is some of the code:

The top of my ListView looks like this:

        <ListView ItemsSource="{Binding ContactsGrouped}" 
        IsGroupingEnabled="True" 
        GroupDisplayBinding="{Binding Key}" 
        GroupShortNameBinding="{Binding Key}" 
        HasUnevenRows="true">

The "Key" refers to

public class Grouping<K, T> : ObservableCollection<T>
{
    public K Key { get; private set; }

    public Grouping ( K key, IEnumerable<T> items )
    {
        Key = key;
        foreach ( var item in items )
            this.Items.Add( item );
    }
}

and my data select looks like this:

        var sorted =
            from contact in contacts
            orderby  contact.FullName
            group contact by contact.FirstInitial
            into contactGroup
            select new Grouping<string, Contact> ( contactGroup.Key, contactGroup );

        ContactsGrouped = new ObservableCollection<Grouping<string, Contact>> ( sorted );

Thanks

-jesse